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Aquatic Biology

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AB 7:31-43 (2009)  -  DOI:

Source populations in coastal crabs: parameters affecting egg production

Augusto A. V. Flores1,*, Cristal C. Gomes2, Wagner F. Villano2

1Centro de Biologia Marinha—Universidade de São Paulo, Rod. Manoel Hipólito do Rego, km 131.5, 11600-000 São Sebastião, São Paulo, Brazil
2Universidade Estadual Paulista, Campus do Litoral Paulista, Unidade de São Vicente, Praça Infante D. Henrique, s/n Parque Bitaru, 11330-900 São Vicente, São Paulo, Brazil

ABSTRACT: Benthic marine invertebrates may form metapopulations connected via propagule dispersal. Conservation efforts often target potential source coastlines to indirectly benefit areas depending on allochthonous offspring production. Besides population density, adult size structure, sex ratio, brooding frequency and the proportion of breeding individuals may significantly influence the reproductive output of benthic populations, but these effects have seldom been tested. We used rocky shore crabs to assess the spatial variability of such parameters at relevant scales for conservation purposes and to test their consistency over 2 consecutive years; we then used the data to address whether bottom-up processes or biological interactions might explain the patterns observed. We decomposed egg production rates into their components for the 2 most abundant brachyuran species inhabiting the intertidal rocky habitat. Adult density and brooding frequency varied consistently among shores for both species and largely explained the overall spatial trends of egg production. Temporally consistent patterns also included among-shore differences in the size of ovigerous females of the grapsid Pachygrapsus transversus and between-bay differences in the fecundity of the spider crab Epialtus brasiliensis. Sex ratio was remarkably constant in both. We found no positive or negative correlations between adult density and brooding frequency to support either the existence of a component Allee effect (lack of mate encounters) or an effect of intra-specific competition. Likewise, shore-specific potential growth in P. transversus does not negatively correlate with frequency of ovigerous individuals, as would be expected under a critical balance between these 2 processes. The patterns observed suggest that bottom-up drivers may best explain spatial trends in the reproductive output of these species.

KEY WORDS: Reproductive traits · Spatial structure · Source areas · Adult benthic populations · Marine conservation

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Cite this article as: Flores AAV, Gomes CC, Villano WF (2009) Source populations in coastal crabs: parameters affecting egg production. Aquat Biol 7:31-43.

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